1. Field of the Invention
The invention relates to a piston for slidable and sealable cooperation with a fluid pressure chamber, and particularly a fluid pressure chamber having an arcuate longitudinal axis.
2. Description of the Prior Art
A piston is conventionally thought of as a cylindrical member having one or more peripheral grooves formed thereon and each groove mounting a piston ring. The rings slidably and sealably cooperate with the cylindrical bore of a cylinder. In the above referred to patent application, and additionally in my co-pending applications, Ser. Nos. 436,412 and 436,852, both filed Oct. 25, 1982, and assigned to the Assignees of this application, there is disclosed an apparatus for extracting heat and/or mechanical energy from a pressured gas wherein a plurality of cylinders are employed defining fluid pressure chambers having arcuate longitudinal axes. Obviously, for a piston to slidably and sealably cooperate with the walls of such a pressure chamber, the ordinary cylindrically shaped piston would not be effective.
It has previously been proposed, for example in Siddons et al. U.S. Pat. No. 3,648,670, to employ a ball or sphere as the piston element in a cylinder having an S-shaped configuration. The employment of a ball does not provide a substantial sealing action between the piston and the wall of the fluid pressure chamber due to the fact that essentially only point contacts are provided between the periphery of the ball and the internal bore of the longitudinally curved fluid pressure chamber. It would obviously be desirable to incorporate a piston ring on a spherical shaped piston in order to improve its sealability, but heretofore no means have been suggested for maintaining such piston ring in proper alignment with the walls of an arcuate axis fluid pressure chamber.